<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,body{
            height: 100%;
            width: 100%;
            background-color: gainsboro;
        }
        div{
            height: 150px;
            line-height: 150px;
            font-size: 100px;
            /* 字体间距 */
            letter-spacing: 20px;
            color: gainsboro;
            /* 文字加粗 */
            font-weight: 700;
        }
        .ao{
            text-shadow: 
            1px 1px 1px white,
            -1px -1px 1px black;
        }
        .tu{
            text-shadow: 
            1px 1px 1px black,
            -1px -1px 1px white;
        }
    </style>
</head>
<body>
    <div class="ao">
        我是凹起的文字
    </div>
    <div class="tu">
        我是凸起的文字
    </div>
</body>
</html>